PRONTOX – A prospective randomized clinical trial for the treatment of lung cancer patients at the University Proton Therapy Dresden

Patients with advanced lung cancer have a low overall survival despite treatment. Radiotherapy treatment is often lim-ited by the toxicity in the surrounding healthy tissue of the lung, oesophagus, spinal cord and heart. The prospective randomized clincial trial PRONTOX (NCT02731001) aims on the analyses of toxicities in patients treated for advanced lung cancer with either photon therapy or proton therapy. Only patients with tumor motion <10 mm are included. Photon and proton treatment plans are created based on time-resolved computed tomography (4D CT) imaging. Both plans are independently evaluated by experienced physicians for their applicability. If both treatments are deemed acceptable in terms of dosimetric parameters, randomization is executed. The dosimetric analysis includes the evaluation of the individual tumour motion and the uncertainties in range (3.5 %) and set-up (±3 mm) for the proton therapy treatment. End of March 2017, three patients were included, of which 2 had already finished their treatment getting double-scattered proton therapy. For the three patients, tumour motion was negligible and had only small effects on the dose distribution. The additional uncertainty analyses revealed the robustness of the generated proton therapy plans against the individual motion (maximum motion amplitude < 2 mm) as well as range and set-up uncertainties. During the treatment, respiratory surrogate signals were recorded for evaluation of breathing variabilities. In addition, control 4D CT were acquired once a week during treatment according to the trial protocol. Based on this imaging, changes in the patient anatomy and tumour motion were assessed. For the two patients who already completed treatment, the effect of anatomical changes and tumour motion changes on the fractional and accumulated dose distribution was small. No intervention e.g. a treatment plan adaptation was required in any case. Follow-up showed no recurrence and no side effects for these two patients so far.